1. Field of the Invention
The present invention relates to a motorcycle, and more specifically, to a body frame structure of a motorcycle.
2. Description of Related Art
In a conventional mono backbone type body frame structure of a motorcycle, a main frame that suspends an engine of the motorcycle extends from a head pipe to the rear in a vehicle width center, bends downward at a rear side of the engine, and reaches a vehicle bottom. Side plates are separately attached to right and left sides at a bottom end portion of the main frame, and a front end portion of a swing arm is supported between the side plates and the main frame.
JP-A-2007-118865 discloses a motorcycle having such a body frame structure. In this motorcycle, right and left side plates are secured by bolt to a main frame in the center. Two bosses (top and bottom) extend from the right and left side plates to abut onto the main frame, thereby adjusting a space between the main frame and the side plates.
However, in this conventional mono backbone type body frame, the right and left side plates are jointed by patching them using the bosses and the main frame. Therefore, in order to smoothly receive a load added to one side plate by the entire body frame including the right and left side plates and the main frame, and to exert sufficient vehicle rigidity, special actions such as increasing the thickness of the main frame or the boss diameter of the side plate are required.